The indoor ventilating device (indoor ventilator) in general is a prerequisite equipment of modernized housing such as skyscraper and apartment where the dirty air in the closed space such as bathroom, kitchen, toilet, etc. of said housing may be exhausted out of the door through installing the said indoor ventilating device, i.e. the said device is installed on the ceiling of indoor closed space to be connected to the air pipe communicating with the common windpipe installed in the said housing. When the motor of said device is started, the indoor dirty air can be exhausted out of the door through the said air pipe and common windpipe so as to achieve the purpose of freshening the air.
Since the said conventional indoor ventilating device (indoor ventilator) and its accesory, i.e. the air pipe, are designed inappropriately, the noise is always generated to trouble the people very much who are eager to live in a very calm environment. The generation of said noise may be attributed to the following causes:
1. The mechanical noise generated by the motor for the indoor ventilating device; It is resulted from the said motor without strict quality control or used for a long time, the wearing of said motor leads to the bearing coming off, or the dynamic balance between the rotating blades and the bearing center of said motor has not been well adjusted. However, such a mechanical noise may be eliminated through the strict quality control during manufacturing process and the improvement of the strength of the material of the said motor. This point is not the subject matter to be solved by the present invention.
2. The whistling noise of shock wave from the undesirably designed air pipe; it is resulted from the said pipe for the conventional indoor ventilating device which is contrary to the principle of gas dynamics. For the modern people eager for a quiet living environment through positively improving the noise pollution, this whistling noise is really very troublesome.
The present invention is designed to eliminate the whistling noise always derived from the said indoor ventilating device. The present inventor, based on his findings from engrossed study of both structural and gas dynamics for a number of years, developed an improved air vent throat of indoor ventilating device capable of preventing noise for bettering the whistling phenomenon of said device and the drawback of outdoor dirty air flowing back to the closed space indoors.